javascript - 对象数组的 lodash 总和

Question

我刚刚开始学习 lodash，并尝试将其合并到我的代码中。正如您所看到的，我正在添加员工下每个元素的权重。问题是我遇到的问题是我不确定如何将第三个元素“性别”放入我的最终数据数组中。我用过这个Reduce array of objects on key and sum value into array构建我的 lodash 代码。您可以在下面看到我如何尝试获取输出。

var userAns = [{
    id: 1,
    text: "answer1",
    employee: [{
        name: "John",
        weight: 3,
        gender: "male"
      },
      {
        name: "Sally",
        weight: 4,
        gender: "female"
      }
    ]
  },
  {
    id: 2,
    text: "answer2",
    employee: [{
        name: "John",
        weight: 6,
        gender: "male"
      },
      {
        name: "Sally",
        weight: 3,
        gender: "female"
      }
    ]
  }
];

var scores = [];
for (var i = 0; i < userAns.length; i++) {
  for (var j = 0; j < userAns[i].employee.length; j++) {
    scores.push(userAns[i].employee[j]);
  }
}

var result = _(scores)
  .map('name')
  .uniq()
  .map(function(key) {

    return {
      name: key,
      score: _(scores).filter({
        name: key
      }).sumBy('weight')
    };
  })
  .value();

console.log(result);

<script src="https://cdn.jsdelivr.net/lodash/4.14.1/lodash.min.js"></script>

这是我尝试获取数组的方法

[
  {
    "name": "John",
    "score": 9,
    "gender": "male"
  },
  {
    "name": "Sally",
    "score": 7,
    "gender":"female" 
  }
]

Answer 1

使用 lodash:

您可以使用 _.flatMap() 的组合, _.groupBy() , _.map()和 _.mergeWith() :

var userAns = [{"id":1,"text":"answer1","employee":[{"name":"John","weight":3,"gender":"male"},{"name":"Sally","weight":4,"gender":"female"}]},{"id":2,"text":"answer2","employee":[{"name":"John","weight":6,"gender":"male"},{"name":"Sally","weight":3,"gender":"female"}]}];

var result = _(userAns)
  .flatMap('employee') // create an array of all emplyoees
  .groupBy('name') // create groups of employees with the same name
  .map(function(g) {
    // merge each group to a single object, and combine weight values
    return _.mergeWith.apply(_, [{}].concat(g, function(obj, src, key) {
      return key === 'weight' ? (obj || 0) + src : undefined;
    }));
  })
  .value();
  
console.log(result);

<script src="https://cdnjs.cloudflare.com/ajax/libs/lodash.js/4.17.4/lodash.min.js"></script>

使用 ES6:

使用Array#map获取 employee 数组的数组，并按 spreading 展平进入Array#concat 。 Reduce数组变成 Map ，然后通过扩展 Map#values 转换回数组迭代器:

const userAns = [{"id":1,"text":"answer1","employee":[{"name":"John","weight":3,"gender":"male"},{"name":"Sally","weight":4,"gender":"female"}]},{"id":2,"text":"answer2","employee":[{"name":"John","weight":6,"gender":"male"},{"name":"Sally","weight":3,"gender":"female"}]}];

const result = [...
  [].concat(...userAns.map(({ employee }) => employee)) // combine all employees to a single array
  .reduce((m, o) => { // reduce similar employees to a single object in a Map, and combine weight
    // if the name object doesn't exists create a new one by cloning the object, and assigning weight: 0
    m.has(o.name) || m.set(o.name, Object.assign({}, o, { weight: 0 }));
    
    m.get(o.name).weight += o.weight; // add the current weight to the name object
    
    return m;
  }, new Map())
  .values()]; // get the Map values, and spread to convert to array
  
console.log(result);